THE INTERACTION OF A COATED TARGET AND AN IMPINGING WATERDROP

The work deals with the evolution of the stresses and the damage in ta rgets with thin protective layers due to perpendicular high-velocity w aterdrop impacts. The analysis involves a modeling of the impact in th e liquid and the solid, and exploration of possible damage mechanisms in the coating and the substrate. We identify three state of stresses that can produce damage, radial tensile stresses that propagate on the surface of the coating, subsurface shear stresses that develop at the coating-substrate interface, and bending stresses near the inner face of the coating. The patterns of these stresses and the locations wher e they develop are in good agreement with experimental findings. The i ntensities and the impulses of the stresses are related to the impact velocity by a power-law rule reminiscent of the one used in experiment ally motivated damage criteria. We find that the peak of the tensile s tresses propagates on the surface of the coating at the speed of the R ayleigh wave in the substrate. The possible role of the subsurface she ar stresses in the evolution of damage in coated targets is also discu ssed. (C) 1998 Elsevier Science S.A. All rights reserved.